The background of the present invention is the field of beverage production system using capsules which contain beverage or other comestible (e.g. soup) ingredients. By means of an interaction of these ingredients with a liquid, a beverage such as coffee or tea can be produced. The interaction can be for example a brewing (e.g., extraction) or dissolution process. Such a capsule is particularly adapted to contain ground coffee in order to produce a coffee beverage by having hot water under pressure enter the capsule and draining a coffee beverage from the capsule.
Systems and methods for obtaining beverages from substances containing capsules are known, for example, in EP-A-512470. Patent application EP 1 654 966 proposes an improvement for providing better sealing upon closure of the extraction system so as to better control the extraction characteristics, particularly the opening and extraction pressures. To do that, the capsule is equipped with an attached seal or a seal that forms an integral part of the cartridge so that each new brewed capsule seals perfectly into the extraction system, thereby avoiding any risks of water leaking and bypassing through the cartridge nip to the outside. An advantage of the invention is that it provides a renewed seal each time a capsule is used. Another advantage is that it allows the capsule to be released more easily by preventing the capsule from “sticking” in the capsule cage through the effect of suction or vacuum. To do that, the invention may provide air passages such as grooves on the pressing edge of the capsule cage.
However, one problem of the device is that when water is injected in the brewing unit, when no capsule is present, and since the brewing unit does not close in a liquid impervious manner, the unit will leak in an uncontrolled manner through the nip.